Published May 23, 2013
A preliminary UB study has found that although trained athletes derive performance benefits from caffeine, most sedentary or lightly active adults do not like exercise more—or perceive their exertion to be less—when given caffeine.
What caffeine does do, according to the study, is make them exercise for longer periods, which could increase their likelihood of achieving the American College of Sports Medicine recommendations for physical activity.
The study, “Acute and chronic caffeine administration increases physical activity in sedentary adults,” was posted online in Nutrition Research on May 10. A pdf of the study is available here.
Its authors are graduate students Patrick Schrader and Leah M. Panek, and Professor Jennifer Temple, all from the Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions.
“What is important about this study,” says Temple, “is that it indicates that the ergogenic (performance-enhancing) properties of caffeine are quite different for trained athletes than for sedentary adults.”
Previous studies with athletes have found that caffeine enhances their performance and reduces their scores on the rated perceived exertion scale, or RPE. The UB researchers hypothesized that caffeine ingestion would have the same effect on sedentary adults; that is, it would increase their capacity for physical exertion by eliminating fatigue symptoms and reducing their perception of exertion while exercising.
The researchers found, however, that:
The study involved 35 subjects between the ages of 18 and 50, half men and half women, who attended eight laboratory sessions, 60 to 75 minutes in length, over the course of two weeks. All were asked to abstain from caffeine for 24 hours before each session and to refrain from engaging in physical activities on the day of their visits.
At each session, half the participants were given caffeine (3 mg/kg) and half a placebo in a sports drink. At the sessions, participants completed treadmill walking at 60 percent to 70 percent of their maximal heart rate at baseline and for six of the seven subsequent visits. To investigate the potential synergistic effects of acute and chronic caffeine on self-determined exercise duration, participants were re-randomized to either the same or different condition for the last (or eighth) visit, creating four chronic/acute treatment groups (placebo/placebo, placebo/caffeine, caffeine/placebo, caffeine/caffeine). That is, they received placebo all along, then caffeine at the last session; placebo all along and placebo at the last session, etc.
At each visit, participants rated how much they liked the activity and how much exertion they thought they had expended. The length of their self-determined exercise sessions also was recorded and analyzed.
The researchers say their future efforts will focus on whether there are dose-dependent effects of caffeine on exercise liking and RPE in sedentary adults, and whether a longer training period might have been necessary to see significant effects of caffeine on liking of exercise and RPE.
“Once we have good data on the most effective dose of caffeine and period of caffeine/exercise pairing,” says Temple, “we hope to determine if caffeine paired with exercise can be used outside the laboratory to make sedentary individuals more likely to be physically active.”